On-demand digital versatile disc DVD manufacturing systems for use in retail environments, centralized fulfillment centers and replication factories require high-speed recording of video content to dual layer DVD recordable media. There are two format types allowed in the DVD Read Only Specifications for dual layer media. In the parallel track path (PTP) case, both layers are recorded and played back from the inner radius toward the outer radius of the disc. In the opposite track path (OTP) case, the layers are recorded and played back in opposite directions with respect to radius. The OTP case allows for continuous playback of content without interruption. Simultaneous recording of both DVD layers utilizing recorders with two optical pickups would greatly improve recording speed and efficiency. This is very difficult to realize because the majority of theatrical or video releases are manufactured on dual layer DVD media recorded in the opposite track path OTP format.
Dual layer DVD opposite track path (OTP) media consists of two layers, layer 0 and layer 1, which are recorded and played back in opposite directions. For recordable media, recording is generally performed in a continuous manner, whereby upon completion of layer 0, the optical pickup will jump to layer 1 and continue the recording process from the same radius, but in the opposite radial direction. In the standard replication process layer 0 masters are recorded from the inside to outside diameter and layer 1 masters are recorded from the outside diameter to the inside diameter. For continuous playback of both layers, the player will first play layer 0 from the inside diameter toward the outside diameter and then the optical pickup head will jump to layer 1 and will seamlessly continue playback of Layer 1 from the outside diameter toward the inside diameter. Direction or rotation sense from the readout side of the disc is the same for both layer 0 and layer 1.
DVD media is recorded and played back in the constant linear velocity (CLV) format. The rotation frequency of the disc for recording and playback processes vary as a function of the radius. This makes it very inconvenient to record both layers simultaneously due to the different rotation frequencies or data rate frequencies required to record layer 0 from inside to outside and to record layer 1 from the outside to inside.
The motion picture and retail industries are looking for a secure means of production of DVD-Video discs that can be produced on-demand from DVD-Video content that is stored on a local server or delivered for central storage server through high speed private networks. This allows for the availability of thousands of DVD-Video titles from a deep catalog of movies that normally could not be easily inventoried in a retail or online store environment. Solutions to support this product segment, however, are only single layer media with a data capacity of 4.7 GB is employed. The data capacity limitation of Single Layer media limits the storage capacity available to store compressed video files and thus limits the video capacity and quality. Furthermore, there is limited storage capacity available for added value features that can be included on product manufactured With the standard DVD-Video replication process. Dual layer media, with its 8.5 GB storage capacity, is highly desired for this purpose because of the high video quality that can be achieved through the use of a high bit-rate. Also, with dual layer media value added features can be included similar to that offered by standard DVD-Video product produced on Dual Layer DVD-9 media.
Higher speed recording is required for an on-demand manufacturing system for both increased throughput and reduced manufacturing cost. For an in-store on-demand replication application, reduced cycle times are desired to improve delivery time to the customer. For single optical pickup recording, dual layer DVD recording can take approximately 15 minutes. Known multiple optical heads in optical disc storage devices use the multiple heads in a non-synchronized manner to improve data recording and retrieval rates and for improved data access time for the device. However, a faster recording time is needed to attract consumer use of in-store, on-demand replication services.